1. Field of the Invention
The present invention relates to a vibration wave motor constructed to frictionally drive a movable member contacting to a vibration member by generating a vibration wave in the vibration member by an electro-mechanical energy converting vibration element (for example, piezoelectric element or electrostrictive element), and more particularly to technology for improving wear resistance of the movable member.
2. Related Background Art
A vibration wave motor has been disclosed by many prior art publications (for example, Japanese Laid-Open Patent Application No. 29192/1977, U.S. Pat. No. 4,580,073 and U.S. Pat. No. 4,587,452). Since the vibration wave motor is essentially driven by frictional drive, the drive force of the vibration wave motor largely depends on the product MW, where W is the pressure force to press the movable member into contact with the vibration member and M is the coefficient of friction. Thus, the vibration member and the movable member are required to be made of a combination of materials having large coefficients of friction M and also to be of low wear. A combination of materials which meets such a requirement is a movable member comprising pure aluminum or an aluminum alloy coated with hard alumite film and a vibration member comprising brass coated by flame spraying a film mixture of tungsten carbide and cobalt (WC-Co 12%) (U.S. patent application Serial No. 921010 filed Oct. 21, 1986).
However, such a combination still has the disadvantage that wear of the alumite film is large.